I'm not sure how different this is, but the Gravity Recovery and Climate Experiment [0] is planning is 3rd mission after 2 currently operating pairs of satellit

I'm not sure how different this is, but the Gravity Recovery and Climate Experiment [0] is planning is 3rd mission after 2 currently operating pairs of satellites using interferometry to map gravity anomalies, among other things. [0]https://en.m.wikipedia.org/wiki/GRACE_and_GRACE-FO https://en.m.wikipedia.org/wiki/GRACE_and_GRACE-FO